a) Field of the Invention PA1 b) Description of Related Art PA1 2) a primary flyback voltage comparator circuit, monitoring PA1 3) a reset signal provided at a reset signal output port for the duration a spark is created across the gaps; and PA1 4) comparing the output of the ionic current computing circuit to a reference voltage obtained through a reference voltage stabilizing circuit.
The present invention pertains to an apparatus for determining the state of combustion within internal combustion engines which use an ignition coil as part of its ignition system.
A known ignition system for internal combustion engines is shown in FIG. 5. The system includes an ignition coil 10 having a primary winding 12 and a secondary winding 14. On the primary side of the ignition coil 10, a power supply unit 2 is connected to a first end of the primary winding 12 and an ignition timing control means 4 is connected to a second end of the primary winding 12, thereby forming the primary circuit. A known ignition timing control means 4 includes a transistor with the collector connected to the second end of the primary winding 12, the emitter connected to ground, and the base connected to an ignition signal input port 6. On the secondary side of the ignition coil 10, spark plug gaps 20,22 are provided between the secondary winding 14 and ground.
The known ignition system operates when the primary side of the ignition coil 10 is "opened", i.e. when current does not flow from the emitter to the collector. When the ignition signal input port 6 receives an ignition signal, the flow of current from the emitter to the collector occurs, thus the "primary" current flow through the primary winding 12.
As is well understood, the interruption of primary current flow through the primary winding 12 induces a secondary voltage in the secondary winding 14. Ignition is possible when the secondary voltage exceeds the breakdown voltage across the gaps 20,22, and a sufficient spark is created to ignite a mixture of fuel and air under compression. Such a spark is created at the instant the primary current flow ceases after reaching a predetermined level. FIGS. 6(a) and 6(b) show primary current flow and secondary voltage, respectively. The vertical dashed lines extending between the designated portions of FIG. 6 identify common points in time to compare and relate the different parameters.
The known ignition system, designed only to provide ignition to an internal combustion engine, is not capable of analyzing performance. For example, it is desirable to determine the state of combustion, e.g. whether combustion has or has not occurred. However, the known ignition system is not capable of determining whether an ignition signal at the input port 6 has in fact created a spark across the gaps 20,22, or whether the fuel and air mixture has actually been ignited by a spark.